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Biomedical subjects

N S Chu

Publications and source records attributed to N S Chu.

At least 109 records · Page 6Linked to original sources
PubMed1987

Thermosensitivity of dorsal raphe neurons in vitro.

Thermosensitivity of raphe neurons was studied in tissue slices of rat brainstems (400-500 micron). Measurement of activity of single cells in the dorsal raphe region of the slices revealed that the majority of neurons (89%) were sensitive to changes in temperature. Over the range 34 to 42 degrees C, 3 classes of thermosensitive cells were found: warm (61%), cold (15%) and biphasic type cells (13%). Many dorsal raphe neurons may be intrinsically temperature sensitive and may serve as extrahypothalamic thermodetector components in the integrative process of central thermoregulation.

Animals↗
PubMed1987

Short- and long-latency tibial somatosensory evoked potentials in cerebral lesions affecting Rolandic leg areas.

Short- and long-latency tibial somatosensory evoked potentials (SEPs) were studied in nine patients with clinical presentation primarily involving one lower extremity. In group 1, with extensive infarcts in the territory of anterior cerebral artery, tibial cortical SEPs were uniformly absent. In group 2, with small infarcts involving Rolandic leg areas, tibial SEPs showed a decrease in overall response amplitude and attenuation of P40. In group 3, with discrete mass lesions compressing Rolandic leg areas, P40 was preserved but might be delayed. Late SEP components (N75, P100 and N135) tended to be preserved in the patients of group 2 and 3. The data suggest that Rolandic leg areas and the neighboring cortex are crucial for short- and long-latency tibial cortical SEPs and that small lesions affecting Rolandic leg areas tend to affect short- and mid-latency SEP components.

Adult↗
PubMed1987

Brain-stem auditory evoked potentials in different types of hepatic diseases.

Brain-stem auditory evoked potentials (BAEPs) were studied in 69 patients with different types of hepatic diseases. BAEPs were normal in viral hepatitis, but the peak V and interpeak I-V latencies were prolonged in liver cirrhosis. Prolongation in peaks III, IV and V and interpeaks I-III, III-V and I-V were observed in both alcoholic liver disease and Wilson's disease with the latter more severely affected. The present data indicate that BAEPs may be used to study the effect of various hepatic diseases on the CNS.

Adult↗
PubMed1987

Pattern-reversal visual evoked potentials: latency changes with gender and age.

Pattern-reversal visual evoked potentials were studied in 123 volunteers with ages ranging from 20 to 77 years. The major positive component (P100) showed a shorter mean latency but a higher mean amplitude for females than males. The age-dependent increase in mean P100 latency was observed in the female group but not in the male group. The present data suggest that gender is more important than age in affecting the P100 latency.

Adult↗
PubMed1986

Median and tibial somatosensory evoked potentials. Changes in short- and long-latency components in patients with lesions of the thalamus and thalamo-cortical radiations.

Alterations in short- and long-latency components of median and tibial somatosensory evoked potentials (SEPs) were studied in patients with lesions in the thalamus and thalamo-cortical radiations. When the lesions were located primarily in the ventro-posterior thalamus, the SEP changes consisted of the following combination: absence of response; decrease in response amplitude; delay in peak latency; and attenuation of median N20-P25 and tibial P40. The laterally situated ventro-posterior lesions tended to preferentially affect tibial SEPs whereas the medially situated lesions tended to preferentially affect median SEPs. The lateral thalamic lesions affected primarily the long-latency SEP components, whereas the medial thalamic lesions affected primarily the mid-latency or the mid- and long-latency SEP components. Corona radiata infarcts produced SEP changes similar to those with the ventro-posterior thalamic lesions except that absence of evoked responses was not observed. Subcortical infarcts tended to affect the mid- and long-latency SEP components with relative preservation of the short-latency components. The present data indicate that only the lesions involving the primary thalamic relay area affected all SEP components, particularly the short-latency components, and that the lesions in other thalamic areas can also influence the SEPs, particularly the mid- and long-latency components. The present study further demonstrates that a combined use of median and tibial SEPs is useful in delineating the topographic organization of the somatosensory system in the thalamus.

Adult↗
PubMed1986

Somatosensory evoked potentials: correlations with height.

Somatosensory evoked potentials (SEPs) to median and posterior tibial nerve stimulation were studied in 160 subjects aged 20-90 years. Height was highly correlated with latencies of spinal and cortical SEPs (N13, N20, N22, and P40). Although tibial central conduction (N22-P40) was also highly correlated with height, median conduction (N13-N22) was not correlated with the latter. Multiple correlation and regression analysis showed that except for the median N13-N20 latency, height provided the best prediction of the remaining SEP latencies. Age alone was not correlated with SEP latencies, but its significance was observed when age and height were considered together as the predictors. Effects of age and height on SEP latencies were independent of gender. The present data indicate that except for the N13-N20 conduction, height is the most important parameter for SEP latencies and can be used for construction of normograms.

Adult↗
PubMed1986

Sensory evoked potentials in Wilson's disease.

Somatosensory, brainstem auditory and pattern-reversal visual evoked potentials (SEP, BAEP and VEP) were studied in 16 patients with Wilson's disease and 16 family members. In 13 patients with neurological manifestations, median nerve stimulation elicited cervical potentials with normal N13 latency. Scalp-recorded components of the median and tibial SEPs were absent bilaterally in 1 patient and unilaterally in another. The median conduction time (N13 to N20 peaks) was bilaterally prolonged in 3 patients and unilaterally prolonged in 5. In the tibial SEPs from 9 patients with neurological symptoms, the N22 latency of the lumbar evoked responses was within normal limits, but conduction time from N22 to P40 peaks was unilaterally prolonged in 5. Overall, 9 of 13 patients with neurological manifestations had SEP abnormalities. The BAEPs were bilaterally abnormal in 12 of 13 patients with neurological symptoms, mainly due to prolongation in the III-V and I-V intervals. In the VEPs from 8 patients with the neurological form, the P100 latency was delayed bilaterally in 2 patients and unilaterally in 1. Abnormalities in evoked potentials were not observed in 3 patients with other forms of Wilson's disease and in the family members. The present study indicates that the majority of the patients with neurological manifestations had subclinical dysfunction in three major sensory pathways. They are consistent with neuropathological and neuroradiological findings of widespread degeneration of the brain in Wilson's disease.

Adolescent↗
PubMed1985

Somatosensory evoked potentials in hepatic encephalopathy.

Median nerve somatosensory evoked potentials were recorded from 33 patients with various degrees of hepatic failure and from 10 age-matched controls. Within 20 ms poststimulation, one negative peak (N13) could be recorded from the middle of the back of the patient's neck at the C2 vertebral level. Within 150 ms, three negative and three positive peaks, sequentially designated as N1, P1, N2, P2, N3, and P3, could be recorded from the scalp over the contralateral sensory cortex. There was a progressive prolongation of peaks and interpeak latencies correlating with the severity of hepatic encephalopathy. In 10 patients with hepatic failure but no clinical evidence of hepatic encephalopathy, latencies of peak N3 and P3 were delayed and N1-N3 interpeak latencies were prolonged. Thirteen patients with grade 1 or 2 hepatic encephalopathy showed further delayed latencies of peaks P2, N3, and P3, further prolonged N1-N3, N1-P2 interpeak latencies, and distortion of waveforms. Peaks N2, P2, N3, and P3 were further delayed, and even disappeared in 10 patients with grade 3 or 4 hepatic encephalopathy. However, central conduction time (N13-N1 interpeak latency) was not prolonged in all stages of hepatic failure. In addition, serial somatosensory evoked potential studies correlated well with the clinical course. The present data suggest that somatosensory evoked potential recording is a reliable objective method in the early assessment and monitoring of hepatic encephalopathy.

Adolescent↗
PubMed1985

Erb's and cervical somatosensory evoked potentials: correlations with body size.

Median and ulnar Erb's (N9) and cervical (N13) somatosensory evoked potentials were correlated with height, arm span, arm length, and Erb's length. All body measurements had high correlations with the N9 and N13 latencies. The highest correlation was obtained between the N9 latency and Erb's length. The N13 latency was correlated higher with height than with arm length. The data suggest that height can be used to construct normogram correlating with the N13 latency.

Adult↗
PubMed1985

Age-related latency changes in the brain-stem auditory evoked potentials.

The effects of age on the brain-stem auditory evoked potentials were studied on 156 healthy subjects with ages ranging from 18 to 76 years. The latencies of peaks I-VII and the interpeak latencies of I-III, III-V and I-V were consistently shorter for the female group than the male group. The females also had higher peak amplitude than the males. The effects of sex on the peak and interpeak latencies were observed in all age groups. There was a small progressive prolongation in the peak latency with increasing age, particularly peak V. Although a correlation between the age and the I-III interval was not observed, there was also a small increase with age in the interpeak latencies of III-V and I-V.

Adolescent↗
PubMed1985

Computed tomographic correlates of auditory brainstem responses in alcoholics.

A previous study has shown a high incidence of abnormal auditory brainstem responses in alcoholics, particularly when cerebral and/or cerebellar atrophy was present in CT scans. To correlate the electrophysiological findings with definable morphological alterations, quantitative measurements of the brainstem structures in CT scans were made. To determine the relative size of the brainstem, the ratio between the sizes of the brainstem and its cisterns was obtained at the midbrain, upper and lower pons. When compared to the aged-matched control group, the alcoholics as a whole and the alcoholics with abnormal auditory brainstem responses had a decrease in the ratio at all three brainstem levels, but these ratios were not decreased in the alcoholics with the normal auditory brainstem responses. The present data indicate that abnormal brainstem responses in the alcoholics correlated with an increased size of the brainstem cisterns and possible brainstem atrophy.

Adult↗
PubMed1985

Somatosensory evoked potentials: monitoring cerebral functions following liver transplantation.

Serial somatosensory evoked potentials (SEPs) were obtained from a patient with Wilson's disease who had had liver transplantation. Correlating with recovery of hepatic encephalopathy and liver functions following the surgery, SEPs showed progressive normalization of peak latencies and waveforms. The data indicate that SEP may be a useful objective method in assessing recovery of cerebral functions following liver transplantation.

Adolescent↗
PubMed1984

Responses of midbrain raphe neurons to ethanol.

The effects of ethanol on single midbrain raphe neurons were studied in the rat. For dorsal raphe neurons, only the units with rhythmic slow firing were consistently inhibited by ethanol. Those units often exhibited periodic cessation of spontaneous discharges in the initial responses, but later showed a dose-related slowing of discharge rates. Although median raphe neurons were also inhibited by ethanol, their responses consisted of an early tendency to fire more regularly, and then a decrease in spontaneous activity with bursting discharges. The data indicate that ethanol exerts different modes of inhibition on these two functionally different cell groups in the midbrain raphe complex.

Animals↗
PubMed1983

Marfan's syndrome and epilepsy: report of two cases and review of the literature.

Epilepsy associated with Marfan's syndrome is rare. Although previous observations have shown that Marfan's patients with epilepsy had angioid streaks in the retina or coloboma of the iris, such ocular manifestations were absent in two patients reported here. One patient with mental retardation and lumbosacral meningocele had generalized seizure. Another patient with sinus bradyarrhythmia and prolapsed mitral valve had partial seizure with secondary generalization. This report and review of the literature suggest that epilepsy in Marfan's syndrome can be due to primary CNS disorders or secondary to disorders of connective tissue.

Adult↗
PubMed1983

Effects of ethanol on rat cerebellar Purkinje cells.

The effects of ethanol on cerebellar Purkinje cells were studied in awake rats immobilized and mechanically ventilated. Single unit activity of 58 cerebellar Purkinje cells was observed for 1 to 8 hr following a single intraperitoneal administration of ethanol doses ranging from 0.25 g/kg to 3.0 g/kg. The alteration in Purkinje cell activity was related to the dose and the blood level of ethanol. Low doses of ethanol tended to excite and high doses tended to inhibit the spontaneous activity of Purkinje cells. At the peak levels of blood ethanol, cerebellar Purkinje cells often exhibited rhythmic short bursting discharges and the periodic intense activation followed by suppression. In contrast to previous observations that actions of ethanol were short, the present data indicate that cerebellar Purkinje cell activity was continuously affected for a few to several hours following a single dose of ethanol. The data are compatible with behavioral observations that impaired coordination in acute ethanol intoxication also had a similar time course.

Animals↗
PubMed1982

Auditory brain stem responses in chronic alcoholic patients.

Auditory brain stem responses (ABRs) were obtained from 66 chronic alcoholic patients. Forty-one percent of the patients had abnormal ABR indicated by prolonged interwave intervals. The incidence of brain stem abnormalities was related to age, the type and number of alcoholic neurological complications, and cerebral atrophy in computerized tomographic (CT) scan. There was a progressive increase in the incidence of abnormal ABRs with age and the number of alcoholic neurological diseases. Among the neurological complications of alcoholism, patients with cerebellar degeneration had the highest incidence of abnormal ABRs (83%). There was a high correlation between cerebral atrophy in CT scan and abnormal ABRs. The data suggest that laboratory methods such as the ABR and CT scan are useful in evaluating the extent of CNS abnormalities in alcoholic patients.

Adolescent↗
PubMed1981

Prevention of alcohol withdrawal seizures with phenytoin in rats.

The efficacy of phenytoin in the prevention of alcohol withdrawal seizures was studied in rats. Phenytoin was administrated together with and again 12 hr after the last dose of chronic alcohol feeding. Protection against alcohol withdrawal seizures was not observed when phenytoin serum levels were below 8 micrograms/ml. However, with phenytoin serum levels between 8-25 micrograms/ml, only 1 out of 32 rats had alcohol withdrawal seizures.

Acoustic Stimulation↗